The government-funded "Open Letter" memorial is designed to honour those currently serving and commemorate veterans affected by the British military's ban on LGBTQI officers, which was lifted in 2000 - 33 years after male homosexuality was partially decriminalised in England and Wales.
A bronze sculpture, it resembles a crumpled free-standing letter containing words from personal messages that were used as evidence to incriminate individuals.
Charles, the commander-in-chief of the British armed forces, is expected to lay flowers at the National Memorial Arboretum in Staffordshire.
Claire Phillips, a lesbian brigadier who joined the army in 1995 when being openly gay was still banned, said the memorial's design resonated deeply with her and is "such an amazing way of representing people who are so incredibly damaged by the ban".
"This design uses the words of our veterans and service personnel to describe how it felt to be subject to the ban ... to begin that process of reconciliation," she told Sky News.
"I'm just deeply, deeply honoured to be here today."
Alastair Smith, a gay sergeant who joined the army in 1998, told Sky News that while it took time for attitudes to change in the army, he had not faced any prejudice there, but had done so in civilian life.
"There are people from the LGBT community who have that gusto, that determination and that drive to perform for their country despite whatever insurmountable odds they may face elsewhere," he said.
The unveiling of the memorial follows recommendations from an independent investigation commissioned by the British government, which reported systemic abuse, including sexual assault and dismissal of LGBTQI service members.
The government has offered financial redress of up to 70,000 pounds ($A144,000) to those impacted.
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